Polyimides have excellent electrical and mechanical characteristics and a high heat resistance of 300° C. or more and, hence, are regarded as useful for applications as surface protection films for semiconductor devices, interlayer insulating films, wiring protection insulating films for circuit boards. In addition, because resist materials are used for circuit formation for semiconductor integrated circuits and multilayer printed wiring boards, the processes therefor are complicated and varied, ranging over film formation on substrates, exposure on predetermined sites, removal of unnecessary sites by etching, cleaning operations for substrate surfaces, and the like. In this regard, photosensitive resin compositions have recently been used more often as permanent resists for applications in which they are kept remaining as insulating materials even after pattern-forming in order to cut down on processes.
Hitherto, many examples of polyimide-containing photosensitive resin compositions have been reported. Proposed among these is a polyimide-containing photosensitive resin composition that contains an already ring-closed polyimide which is not accompanied by the cure shrinkage of film following a ring closure reaction from a polyimide precursor to a polyimide and that can form a high resolution pattern and a film having an excellent heat resistance (for example, see JP 2011-17897 A).
When a polyimide-containing photosensitive resin composition is used as an insulating film, it is important to form a pattern whose cross-sectional shape is rectangular. This is because a pattern having a reverse tapered cross-sectional shape will cause a defective conduction resulting from the insufficient embedding of a metal working as a conductor, and a forward tapered shape will cause the pattern to be formed on the substrate surface more than necessary.
However, when a material such as aforementioned is used for pattern processing, the light exposure margin is narrow, and it is difficult to obtain a pattern having a rectangular cross-sectional shape.
It could therefore be helpful to provide a photosensitive resin composition that can form a pattern having a high resolution, wide light exposure margin, and rectangular cross-sectional shape and can form a film having an excellent heat resistance.